Thanks everyone, I got my crystals with PEG 8000 at first and after micro-seeding aith PEG 3350.Now I would work with all your suggestions and references with new vigor.
ivan On Thu, Jul 28, 2011 at 9:43 AM, Patrick Shaw Stewart <patr...@douglas.co.uk > wrote: > Ed (and Ivan) > > Peter Sun and colleagues published two papers where they show that > crystallization conditions for protein-protein complexes are strongly > biased towards PEG-based rather than high-salt or > organic-solvent-based conditions. This includes antibody-antigen > complexes. > > http://www.ncbi.nlm.nih.gov/pubmed/16699187 > http://scripts.iucr.org/cgi-bin/paper?do0016 > > I have heard anecdotally that the same is true of protein-peptide and > protein-small molecule complexes, although I don't know of any > systematic study. > > Can anyone shed light on this? > > I guess we can look in the Marseilles database > > Best wishes to all > > Patrick > > > > On Thu, Jul 28, 2011 at 2:32 PM, Ed Pozharski <epozh...@umaryland.edu> > wrote: > > > > On Thu, 2011-07-28 at 05:07 +0100, Sean Seaver wrote: > > > Spoiler - Fabs like ammonium sulfate. > > > > Not really - in my hands the ammonium sulfate was one hit out of 7. > > > > While Ivan's question is about Fab complexes with protein antigen, I > > think it brings up a more general question of protein class-dependent > > crystallization bias. While some general trends exist for classes of > > biopolymers (e.g. MPD is number one precipitant for DNA; protein:DNA > > complexes tend to crystallize in PEG-based conditions), a general idea > > of assigning a preferred precipitant to a protein class is, imho, > > pointless. Fabs are a good example - one would think that with half of > > the protein more or less the same in all instances some general trends > > should exist. And perhaps they do, as this > > > > http://scripts.iucr.org/cgi-bin/paper?S0907444999016224 > > > > seems to suggest. But alas, Fab crystallization conditions, once you > > look into it, appear to be just as diverse as the same for proteins in > > general. Crystallization conditions may change radically upon point > > mutation, so why would one expect that a class of proteins sharing some > > 50% identity will show unusual love for PEG, ammonium sulfate, sodium > > malonate or any other "miracle precipitant"? > > > > Consider this. Thanks to great engineering at the Douglas Instruments, > > we can routinely set up ~1000 drops for a given protein. If one of them > > shows a crystalline shower, we celebrate. To me, the fact that we try > > wrong crystallization conditions 99.9% of the time, proves that any > > attempt to predict crystallization conditions beyond vague things like > > "keep pH close to protein pI", "sodium malonate is cool", "PEG and > > ammonium sulfate are two most successful precipitants in history of > > protein crystallography", etc., is futile. Time wasted on looking into > > what is the most common precipitant for a particular class of proteins > > is better spent on setting up more trays. > > > > Cheers, > > > > Ed. > > > > -- > > Oh, suddenly throwing a giraffe into a volcano to make water is crazy? > > Julian, King of Lemurs > > > > -- > patr...@douglas.co.uk Douglas Instruments Ltd. > DouglasHouse, EastGarston, Hungerford, Berkshire, RG177HD, UK > Directors: Peter Baldock, Patrick Shaw Stewart > > http://www.douglas.co.uk > Tel: 44 (0) 148-864-9090 US toll-free 1-877-225-2034 > Regd. England 2177994, VAT Reg. GB 480 7371 36 >
